The present invention relates to optical diffractometers, and particularly to improvements thereto by including a television camera and cathode ray tube arrangement for displaying images derived from the diffractometer.
Known optical diffractometers essentially comprise three units, a light source, which is normally a laser which produces a coherent light beam, for example a helium-neon laser producing light at 6328 Angstrom units, a transformation unit, in which is located the transparency or other object, and a reconstruction unit which reconstructs the required image of the object. The light source used in such diffractometer systems is normally operated in the TEM.sub.00 mode, and the light emitted from the laser is condensed onto a pin hole by a condenser lens. This arrangement acts to inhibit stray light and to cut out unwanted modes of the laser. The pinhole aperture, or stop, is located in the front focal plane of a lens which acts as a beam expander and collimator, and the object, such as a transparency, is located in a position such that the collimated light falls on the selected area thereof. The light falling on the object is diffracted thereby and the diffracted light is collected by a transform lens and focused at a plane known as the transform plane. The optical information which can be obtained from this plane is important because it represents the Fourier spectrum of the spatial variations of optical transmission across the object. Certain parts of the spectrum can be modified by selectively transmitting part of the light in the transform plane. In this way, periodic or random features present in the object can be illuminated or enhanced as required.
Light passing through the transform plane is focused by an image lens at an image plane at which the image is reconstructed.